To improve network capacity of a service intensive area, in 3GPP (the 3rd Generation Partnership Project), the deployment of small cells has been allowed. An increase in the number of small cells leads to an increase in interference. Due to the small coverage of small cells, which are generally deployed in shopping malls, office buildings, and other locations whose business volume changes with time dynamically, 3GPP is vigorously carrying out the research of small cell switch (that is, on/off) so as to save energy when the amount of business is less and reduce the interference.
Currently, if there are still subscribers in connection with a small cell before the small cell is closed, these subscribers will be forced to switch out or the communication thereof will be interrupted when the small cell is closed and will be restored when the small cell open again.
If the subscribers in connection are switched out before the small cell is closed, it can be achieved via the following two methods: 1), through a Handover (“HO” for short) procedure; 2), through a Secondary service cell (“Scell” for short) removal/addition procedure.
For HO procedure, the subscriber must be switched out successfully in a time period from On to Off of the small cell. The time period from On to Off is relatively long, generally more than 200 ms if a new measurement report is needed to select a target cell, or, generally around 50 ms during which a handover execution process and a handover complication process is performed if no measurement report is needed. Basically, for most of the opening time of the small cell, the subscriber is in the process of handover. Frequent on-and-off switching of the small cell will lead to frequent handover of the subscriber, as a result, the cumulative handover interrupt time is very long while the time for continuous communication is very short, thus make the user experience worse.
For Scell removal/addition procedure, the subscriber has to remove an old small cell at the first place and then add and activate a new small cell. Similar to the HO procedure, it will take a relatively long time to complete the procedure, specifically, generally more than 200 ms if a new measurement report is needed to add a new small cell, or, generally around 30 ms, which is equivalent to the activation time of the new small cell, if no measurement report is needed.
On the other hand, if the communication of the subscriber is interrupted when the small cell is closed and then restored when the small cell opens again, the quality of user communication will be greatly affected. For example, there can be call disconnection, video download pause, etc.
The technical schemes described above will affect the performance of user communication seriously; therefore, a new solution is desired to reduce communication interrupt time due to closing of a transmission point, thus improving user experience, and improving the overall resource utilization and system throughput of the system.